Peroxidase activity in rat tracheal epithelium and gland

Endogenous peroxidase activity in the upper tracheal epithelium and submucosal gland of specific pathogen-free rats was examined cytochemically using the DAB method in animals bred in a conventional room without special equipment for air filtration (conventional system), and those bred under a semibarriered system in which fresh air was filtered and controlled to flow in one way (semibarriered system). Peroxidase activity was consistently positive in the serous cells of the gland of all the rats in both groups. In 22 (71.0%) of the 31 rats in the conventional system, peroxidase activity was demonstrated also in ciliated cells, mucous cells, and goblet cells of the tracheal epithelium, and in mucous cells and duct cells of the tracheal submucosal gland. However, the activity was detected in these cells only in 2 (6.7%) of the 30 rats in the semibarriered system. Goblet cells were not observed in the latter group of rats. The fine localization of peroxidase activity was similar among the peroxidase positive cells, and was demonstrated in the cisternae of the nuclear envelope and rough-surfaced endoplasmic reticulum, some parts of Golgi apparatus, secretory granules, and in some cases in the intraductal spaces of the gland. The present study indicated that environmental conditions markedly influence peroxidase activity in the upper tracheal epithelium and gland of rats.